Imagine that you are asked to remember the number "584". What could be easier? Whether you wanted to or not, the number would be yours to record in a few minutes. With the slightest effort of will you could remember it at the end of this chapter; and, if it were important enough, you would recollect it next month, next year or next century……

Imagine that you are asked to remember the number ‘584′. What could be easier? Whether you wanted to or not, the number would be yours to record in a few minutes. With the slightest effort of will you could remember it at the end of this chapter; and, if it were important enough, you would recollect it next month, next year or next century.

There is an American-let us call him Henry M. – who has been robbed of this precious power to remember; not partially and gradually, just by growing old, as most of us will be; but suddenly and almost totally, by the knife of a well­ intentioned surgeon. From Henry we can learn about the nightmare of eternal forgetfulness – a condition that Franz Kafka would have been delighted to describe. Brenda Milner, at the Neurological Institute, has followed the case of Henry for more than 20 years. She once asked him to try to remember that very number, ‘584′. He sat quietly for 15 minutes, and, to her surprise, could recall the number. But when asked how he did it, this is what he said:

“It’s easy. You just remember 8. You see, 5, 8 and add 4 up to 17. You remember 8; subtract it from 17 and it leaves 9. Divide 9 in half and you get 5 and 4, there you are: 584. Easy!”

Henry lives in a world of his own, restricted not just in space but in time. Ever since an operation on his brain in 1953, his world has been just a few minutes long. Without such elaborate and fantastic tricks of rehearsal, almost everything slips from his mind, like water through a sieve. Every moment has a terrible freshness. He never knows the day of the week, what year it is or even his own age. Even though Brenda Milner has spent countless hours with Henry, she is an utter stranger to him, and on each new occasion that they meet it is as if she were entering his transient world for the first time.

Henry works in a state rehabilitation centre, mounting cigarette lighters on cardboard frames, a task that he has learned to do skilfully. But still he can give no account whatever of his place of work, how he gets there or the type of job that he does. So Henry has not lost the ability to learn new skills of movement; he is, quite simply, unable to remember the new contents of his conscious experience. His general intelligence is not at all reduced and he is painfully aware of his own short-comings. He apologizes constantly for the absence of his mind. ‘Right now, I’m wondering’, he once said, ‘have I done or said anything amiss? You see, at this moment everything looks clear to me, but what happened just before? That’s what worries me. It’s like waking from a dream; I just don’t remember…. Every day is alone in itself, whatever enjoyment I’ve had, and whatever sorrow I’ve had.’

Henry still has his very old memories and habits, but cannot form new ones and even had amnesia for things that happened in the years immediately before the operation. Three years before, his favourite uncle died, but Henry suffers the same grief anew each time he is told of his uncle’s death!

In 1892 the German physiologist Friedrich Goltz described a similar loss of memory in dogs after the cerebral cortex had been damaged. ‘They do not learn from past experience’, Goltz wrote. ‘They do not have experiences, for only he who has memories can have experiences. The decerebrated dog is essentially nothing but a child of the moment’.

Henry is a ‘child of the moment’, too; he is trapped, interminably, in the naiveté of infancy.

We discover from this special case that our memories have two forms: one of them is quickly created but fades within a few minutes, to be followed by a more persistent store, which can last for a lifetime. The most popular view is that short-­term memories are converted or consolidated into the long-term ones, but it is just possible that the two processes are totally independent. One thing seems

certain; the embodiments of the two sorts of memory must be quite different.

Henry has lost the power to form new long-term memories; or perhaps he can make them, but has no way to retrieve them again.

Not remembering can be terrifying — and dangerous. I read somewhere that Alzheimer patients are helped by carrying or wearing a small camera that records what they see and do. After that, I have used my digital camera to help track things that are important to remember. I’ve always been absent-minded, especially under stress.